The maximum unbalanced load is that load that may be placed on a neutral
conductor if one of the legs is deenergized. In single phase, that would be the
A or B legs.
The calculation of maximum unbalanced load is an addition problem. First in
a single phase panel, ignore all 240 volt loads. If one leg goes off, they will
not function. Determine the total of all loads connected to the A leg. Then
determine the total load connected to the B leg.
Which ever is larger, is the maximum unbalanced load.
In the case of three phase, the same procedure is used except that if there
are single phase loads connected to two legs, they must be calculated if both
legs they are connected to remain energized.
So say leg A deenergized. But B and C are still on. Any load connected to
all three legs, three phase loads, are ignored. They will not function if
protected by phase monitors.
This leaves what ever is connected to legs B and C. If there are any loads
connected to AB or AC, ignore them since they will not draw current because A
leg is off. Next, include all loads connected to BC and all loads connected to
just B and to just C.
Compare the totals for B and C. What ever is larger is the maximum
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